Electricity is an essential part of modern life. Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to electrical substations located near demand centres. Transmission lines mostly use high-voltage three-phase alternating current (AC). Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in long-distance transmission. Power is usually transmitted through overhead power lines. Underground power transmission has a significantly higher cost and greater operational limitations but is sometimes used in urban areas or sensitive locations. Most recently, submarine power cables provide the possibility to supply power to small islands or offshore production platforms without their own electricity production. On the other hand, submarine power cables also provide the possibility to bring ashore electricity that was produced offshore (wind, wave, sea currents . . . ) to the mainland.
These power cables are normally steel wire armoured cables. A typical construction of steel wire armoured cable 10 is shown in FIG. 1. Conductor 12 is normally made of plain stranded copper. Insulation 14, such as made of cross-linked polyethylene (XLPE), has good water resistance and excellent insulating properties. Insulation 14 in cables ensures that conductors and other metal substances do not come into contact with each other. Bedding 16, such as made of polyvinyl chloride (PVC), is used to provide a protective boundary between inner and outer layers of the cable. Armour 18, such as made of steel wires, provides mechanical protection, especially provide protection against external impact. In addition, armouring wires 18 can relieve the tension during installation, and thus prevent copper conductors from elongating. Possible sheath 19, such as made of black PVC, holds all components of the cable together and provides additional protection from external stresses.
Since the application environment of these cables is humid or contains moisture, certain corrosion protection for these cables is desired, in particular for submarine cables whose application environment is very corrosive. Because the cable (core) heats up and the corrosion resistance in sea water of the most steel grades strongly degrades with raising temperature, the corrosion protection of the power cables becomes crucial. Therefore, stainless steel or galvanized steel wires are considered to be used as armouring wires in particular for submarine power cables. US patent application 2002/0027012 A1 provides a less expensive substitute solution, where applies a reinforcing wire made of composite steel having a steel core of a standard type covered in a layer of stainless steel.
On the other hand, considering the magnetic fields associated with high voltage submarine cable, CN patent application 101950619A discloses an armouring structure formed by arranging round copper wires and non-magnetic stainless steel wires in alternation. The hybrid armoured layer formed by arranging the round copper wires and the non-magnetic stainless steel wires at intervals one by one can reduce the magnetic losses when used for armouring the submarine cable. However, due to the application of two materials, the production process becomes complex and the fitting of the cable into e.g. sockets may create problems. Moreover, the use of copper makes this armouring structure quite expensive.